Atomistic and multiscale simulations of next generation energy storage systems

锂离子电池是绿色能源技术的核心，有着广泛的应用，从手机和笔记本电脑到电动汽车，甚至储存来自可再生资源的电力。然而，这种技术正在达到它的极限，而我们对容量、功率输出和寿命越来越大的电池的需求意味着我们必须探索和开发下一代储能系统，如Li-Metals、Li-S和Li-O2电池。这些的实际实现取决于稳定的锂金属阳极的可用性。只有准确地从根本上了解和控制锂金属与其周围环境的相互作用，才能使合适的阳极成为可能，从锂加工环境开始，包括(固体或液体)电解液。利用ONETEP程序中线性标度密度泛函理论(DFT)的最新进展，在电解液环境和外部恒电位控制存在的情况下，对金属体系进行多尺度模拟，旨在促进对金属锂阳极的基本理解，并通过计算开发合适的解决方案。特别关注外加电压在改变电极及其钝化层的物理化学性质中的作用。虽然这些课题的初步工作已经开始出现在科学文献中，但电压的作用对于现实模拟是必不可少的，但计算化学和物理学社区还没有详细讨论，所以这是目前学生确定的研究机会。该项目将使用大规模的DFT模拟来探索外加电压对金属锂表面的结构、相对稳定性和电子性质、声子、振动稳定性和弹性性质的作用。它还将研究在钝化的金属锂表面上可能的退化机制和电压相关的锂扩散机制。学生的主要目标是利用模拟来探索金属锂阳极钝化层的抑制电子传导性和抗快速锂离子扩散引起的机械扭曲的困难组合的最佳解决方案。根据锂模拟的进展，还可以探索其他化学物质，如钠基电极。

Li-ion batteries are central to green energy technologies and have a vast range of applications from mobile phones and laptops to electric vehicles and even storing electricity from renewable resources. However this technology is reaching its limits and our increasing demand for batteries with larger capacity, power output and lifetime means that we have to explore and develop the next generation of energy storage systems such as Li-metal, Li-S and Li-O2 batteries. The practical realisation of these rests on availability of stable Li metal anodes. Suitable anodes can only be made possible by accurate fundamental understanding and control of the interactions of Li metal with its surroundings, starting from Li processing environments and including (solid or liquid) electrolytes. Using recent advances in linear-scaling Density Functional Theory (DFT) in the ONETEP program, for multiscale simulation of metallic systems in the presence of both electrolyte environment and external potentiostatic control, this studentship aims to advance the current fundamental understanding of metal Li anodes and computationally develop suitable solutions. Special focus will be on the role of externally applied voltages in altering the physicochemical properties of the electrodes and their passivation layers. While preliminary work on these subjects has started to appear in the scientific literature, the role of voltage is essential for realistic simulations but is yet to be tackled in detail by the computational Chemistry and Physics communities, so this is the identified research opportunity for the present studentship. The project will use large-scale DFT simulations to explore the role of an externally applied voltage for the structure, relative stability and electronic properties of metal Li-surfaces, the phonons, vibrational stability and elastic properties of metal Li-surfaces. It will also investigate possible degradation mechanisms and voltage-dependent Li-diffusion mechanisms at the passivated metal-Li surfaces. The overarching goal of the studentship is to use simulation to explore optimum solutions for the difficult combination of requirements of suppressed electron conductivity and resilience to mechanical distortions induced by fast Li-ion diffusion, for the passivation layers of metal Li-anodes. Depending on progress with the Li simulations, other chemistries could also be explored such as Na-based electrodes.